DHCP question!

[TechyLike]

Why does Microsoft tell you to configure a 30/70 split when running DHCP on two different DHCP servers?

Wouldnt this mean you would hit problems when the "70%" server falls over?

Surely a more logical route would be to make sure you have twice the addresses available than required and do a 50/50 split?

Any help appreciated. Ta.

 

[Whoheard]

Don't take it too serious...everything functions perfectly in a MS world.

It is just a recommendation--probably by some over-paid genius. The split is really up to you. It is really based on the number of users on your network. If you have more than a 1 user to 2 ip's ratio, then you are screwed anyway. But, at least you will have some of the users on the network functioning; and you can get the rest of them online manually or make them wait until the server is back up and running.

Split them as you see fit, but just remember those numbers for the exam. After all, it's not as if the second server does nothing until the first server stops responding. If you have two servers, they both respond equally to requests.

Food for thought.


bob



bob

 

[TechyLike]

Cheers Bob, it makes me feel a little better just having a re-assuring word from someone.

We've since figured out that the Cisco kit will mostly send requests to the first server, funnily enough it looks to be around 70% goes to it so we could be in luck.

Thanks again.

Colin Scott.
Milkinfirst.com

 

[Whoheard]

Thanks. Glad to help.

BTW...
If you are able to sniff the user's connection, you will see that both servers are actually responding to the user's DHCP request. The user generally accepts the first one to respond and ignores the other.

Your seeing of 70% from one server is because of the network design--no design flaws, only congestion of the pathway. If the link/switch/router to the DHCP servers are busy, and the second server happens to respond to the client before the first, the user does not care or discriminate one offer from the other. The client just wants an address.

This same principle holds true for Domain User Login Authentication. During boot up, the users queries DNS for a Domain Controller (DC). DNS will send back a complete list of DC's in which to authenticate. The client does a shotgun search for a DC, and the first one to repond becomes his DC.

Best of luck.

bob